My 130 gallon tank has a 10 gallon tub filter. The water comes in from the bottom, rises up through a layer of pot scrubbers, then the floss on top before exiting the tub back into the tank. All the dirty stuff falls to the bottom.There's a layer of floss on top of the scrubbers and I also put a small sheet across the 3 exit holes for added filtering.

Now my question is this; when it comes time to change it, should I just change the floss that is covering the holes or change the main one that covers the scrubbers?

That would be the opposite of what I have been told in the old forum. People had said the pot scrubbers were good for the good stuff.Tossing that every month would be a huge waste considering it's all plastic.Plus, if I did that, I would destroy everything & start a cycle all over again.

Floss is like a polishing pad; you want to have as much of the solid waste removed first before getting to the floss. Then the floss takes care of the small stuff that wasn't removed before. So it is correct to have it on top of the coarser material.

I treat my floss the same way as the rest of the filtering material when I clean the filter; just rinse it in tank water. However, the floss is more prone to falling apart so I rinse it carefully and do not really squeeze it the way I do with the coarser material.

@Sandman1969 wrote:That would be the opposite of what I have been told in the old forum. People had said the pot scrubbers were good for the good stuff.Tossing that every month would be a huge waste considering it's all plastic.Plus, if I did that, I would destroy everything & start a cycle all over again.

I think you might have misunderstood me,

The floss should go first, removing as much of the solid waste as possible before the water gets to the pot scrubbers. If you let the water go to the pot scrubbers first it will clog your pot scrubbers in no time. The floss can be regularly replaced as it is dirt cheap.

The pot scrubbers should never need changing and only occasional rinsing with tank water. As an example I rinse the pot scrubbers in my large bio-filters about every six months.